Short communication: retinoic acid plus prolactin to synergistically increase specific casein gene expression in MAC-T cells

Mammary alveolar (MAC-T) cells, an established bovine mammary epithelial cell line, are frequently used to investigate differentiation. A lactogenic phenotype in these cells is induced by treatment with a combination of hydrocortisone, insulin, and prolactin (PRL). The effect of the vitamin A derivative retinoic acid (RA), which induces differentiation in many cells, has not been studied in MAC-T cells. The objective of this study was to evaluate the differentiation potential of RA (1 μM) in MAC-T cells and to examine the effect of combined treatment with RA (1 μM) and PRL (5 μg/mL). Although RA treatment alone inhibited MAC-T cell proliferation, co-treatment of RA with PRL increased cell growth compared with the control group (treated with 1 μg/mL hydrocortisone and 5 μg/mL insulin). The ratio of Bcl to Bax mRNA was decreased in the RA treatment compared with RA+PRL or control. Retinoic acid-induced differentiation of MAC-T cells was associated with an increase in the mRNA expression of αS1-casein (3.9-fold), αS2-casein (4.5-fold), and β-casein (4.4-fold) compared with the control group. Expression of αS1-casein, αS2-casein, and β-casein was increased 12.9-fold, 11.9-fold, and 19.3-fold, respectively, following treatment with RA and PRL combined compared with the control group. These results demonstrate that RA induces differentiation of MAC-T cells and acts synergistically with PRL to increase specific casein gene expression.

Folate receptor-mediated boron-10 containing carbon nanoparticles as potential delivery vehicles for boron neutron capture therapy of nonfunctional pituitary adenomas

Invasive nonfunctional pituitary adenomas (NFPAs) are difficult to completely resect and often develop tumor recurrence after initial surgery. Currently, no medications are clinically effective in the control of NFPA. Although radiation therapy and radiosurgery are useful to prevent tumor regrowth, they are frequently withheld because of severe complications. Boron neutron capture therapy (BNCT) is a binary radiotherapy that selectively and maximally damages tumor cells without harming the surrounding normal tissue. Folate receptor (FR)-targeted boron-10 containing carbon nanoparticles is a novel boron delivery agent that can be selectively taken up by FR-expressing cells via FR-mediated endocytosis. In this study, FR-targeted boron-10 containing carbon nanoparticles were selectively taken up by NFPAs cells expressing FR but not other types of non-FR expressing pituitary adenomas. After incubation with boron-10 containing carbon nanoparticles and following irradiation with thermal neutrons, the cell viability of NFPAs was significantly decreased, while apoptotic cells were simultaneously increased. However, cells administered the same dose of FR-targeted boron-10 containing carbon nanoparticles without neutron irradiation or received the same neutron irradiation alone did not show significant decrease in cell viability or increase in apoptotic cells. The expression of Bcl-2 was down-regulated and the expression of Bax was up-regulated in NFPAs after treatment with FR-mediated BNCT. In conclusion, FR-targeted boron-10 containing carbon nanoparticles may be an ideal delivery system of boron to NFPAs cells for BNCT. Furthermore, our study also provides a novel insight into therapeutic strategies for invasive NFPA refractory to conventional therapy, while exploring these new applications of BNCT for tumors, especially benign tumors.

Nitrate ion promoted formation of Ag nanowires in polyol processes: a new nanowire growth mechanism

In polyol processes, it was widely accepted that Ag nanowires (NWs) were formed via uniaxial growth of multiple twinned decahedral particles (MTPs) along the {111} facets. Herein, we show that the above MTP uniaxial growth mechanism for growth of nanorods (NRs) and short nanowires (NWs) is different from that for the growth of long Ag NWs. We provide experimental evidence to show that polycrystalline long Ag NWs (up to ~100 μm) could be formed in high yield (~90%) by a completely different growth mechanism via self-assembly of Ag NPs/NRs. Transmission electron microscope (TEM) measurements show that long Ag NWs are composed of crystalline Ag NPs and NRs with multiple crystal orientations, and many NRs have crystalline structures with pentagonal cross section. Solution phase in situ X-ray diffraction (XRD) measurements show that a strained face-centered tetragonal (fct) phase was gradually formed during the formation and growth of long Ag NWs, in addition to the normal face-centered cubic (fcc) phase. The strained fct phase disappears after partial etching by HAuCl(4) and Fe(NO(3))(3). The working conditions for the MTP uniaxial growth mechanism and the current nitrate-promoted self-assembly growth mechanism will be compared and discussed.

Reusable amperometric biosensor for measuring protein tyrosine kinase activity

This work presents a simple, low-cost and reusable label-free method for detecting protein tyrosine kinase activity using a tyrosinase-based amperometric biosensor (tyrosine kinase biosensor). This method is based on the observation that phosphorylation can block the tyrosinase-catalyzed oxidation of tyrosine or tyrosyl residue in peptides. Therefore, the activity of p60c-src protein tyrosine kinase (Src) on the developed tyrosine kinase biosensor could be quickly determined when its specific peptide substrate, p60c-src substrate I, was used. The tyrosine kinase biosensor was highly sensitive to the activity of Src with a linear dynamic range of 1.9-237.6 U/mL and the lowest detection limit of 0.23 U/mL. Interestingly, the tyrosine kinase activity can be measured using the developed tyrosine kinase biosensor repetitively without regeneration. The inhibitory effect of various kinase inhibitors on the Src activity could be determined on the tyrosine kinase biosensor. Src-specific inhibitors, PP2 and Src inhibitor I, effectively suppressed Src activity, whereas PD153035, an inhibitor of the epidermal growth factor receptor, was ineffective. Staurosporine, a universal kinase inhibitor, inhibited Src activity in an ATP concentration-dependent manner. These results suggests that the activities of tyrosine kinases and their behaviors toward various reagents can be effectively measured using the developed tyrosine kinase biosensor.

Large enhancements in optoelectronic efficiencies of nano-plastically stressed conjugated polymer strands

The photoluminescence (PL) of well dispersed molecules of a conjugated polymer, poly[2-methoxy-5-((2'-ethylhexyl)oxy)-1,4-phenylene-vinylene] (MEH-PPV), in an optically inert matrix manifested dramatic increases when the individual molecular strands were fully stretched. The PL increase rose with stretching and may reach several folds when the mechanical strain of the matrix polymer went beyond 550%. Strong polarization effects indicate that stretching individual polymer chains was responsible for the PL enhancement. This effect was attributed to suppression of electron-phonon interactions in the stress-rigidified polymer chain segments and may be useful for efficiency-enhanced polymer-based optoelectronic devices.

Implanted bone marrow-derived mesenchymal stem cells fail to metabolically stabilize or recover electromechanical function in infarcted hearts

Mesenchymal stem cells (MSCs) have been used with success in several clinical applications for clinical treatment of ischemic hearts. However, the reported effects of MSC-based therapy on myocardial infarction (MI) are inconsistent. In particular, the preventive effects of MSC-based therapy on arrhythmic sudden death and metabolic disorders after infarction remain controversial. Here, we investigated the effects of MSCs on reverse remodeling in an infarcted myocardium, and found that MSC-therapy failed to achieve the complete regeneration of infarcted myocardium. Histological analyses showed that although infarct size and interstitial fibrosis induced by MI recovered significantly after MSC treatment, these improvements were marginal, indicating that a significant amount of damaged tissue was still present. Furthermore, transplanted MSCs had slight anti-apoptotic and anti-inflammatory effects in MSC-implanted regions and no significant improvements in cardiac function were observed, suggesting that naïve MSCs might not be the right cell type to treat myocardial infarction. Furthermore, small ion profiling using ToF-SIMS revealed that the metabolic stabilization provided by the MSCs implantation was not significant compared to the sham group. Together, these results indicate that pretreatment of MSCs is needed to enhance the benefits of MSCs, particularly when MSCs are used to treat arrhythmogenicity and metabolically stabilize infarcted myocardium.

Regulation of xanthine oxidase activity by substrates at active sites via cooperative interactions between catalytic subunits: implication to drug pharmacokinetics

Three xanthine oxidase substrates (i.e., xanthine, adenine, and 2-amino-4-hydroxypterin) show a "substrate inhibition" pattern (i.e., slower turnover rates at higher substrate concentrations), whereas another two substrates (i.e., xanthopterin and lumazine) show a "substrate activation" pattern (i.e., higher turnover rates at higher substrate concentrations). Binding of a 6-formylpterin at one of the two xanthine oxidase active sites slows down the turnover rate of xanthine at the adjacent active site from 17.0 s(-1) to 10.5 s(-1), and converts the V-[S] plot from "substrate inhibition" pattern to a classical Michaelis-Menten hyperbolic saturation pattern. In contrast, binding of xanthine at an active site accelerates the turnover rate of 6-formylpterin at the neighboring active site. The experimental results demonstrate that a substrate can regulate the activity of xanthine oxidase via binding at the active sites; or a xanthine oxidase catalytic subunit can simultaneously serve as a regulatory unit. Theoretical simulation based on the velocity equation derived from the extended Michaelis-Menten model shows that the substrate inhibition and the substrate activation behavior in the V-[S] plots could be obtained by introducing cooperative interactions between two catalytic subunits in homodimeric enzymes. The current work confirms that there exist very strong cooperative interactions between the two catalytic subunits of xanthine oxidase.

Neutron capture nuclei-containing carbon nanoparticles for destruction of cancer cells

HeLa cells were incubated with neutron capture nuclei (boron-10 and gadolinium)-containing carbon nanoparticles, followed by irradiation of slow thermal neutron beam. Under a neutron flux of 6 x 10(11) n/cm(2) (or 10 min irradiation at a neutron flux of 1 x 10(9) n/cm(2) s), the percentages of acute cell death at 8 h after irradiation are 52, 55, and 28% for HeLa cells fed with BCo@CNPs, GdCo@CNPs, and Co@CNPs, respectively. The proliferation capability of the survived HeLa cells was also found to be significantly suppressed. At 48 h after neutron irradiation, the cell viability further decreases to 35 +/- 5% as compared to the control set receiving the same amount of neutron irradiation dose but in the absence of carbon nanoparticles. This work demonstrates "proof-of-concept" examples of neutron capture therapy using (10)B-, (157)Gd-, and (59)Co-containing carbon nanoparticles for effective destruction of cancer cells. It will also be reported the preparation and surface functionalization of boron or gadolinium doped core-shell cobalt/carbon nanoparticles (BCo@CNPs, GdCo@CNPs and Co@CNPs) using a modified DC pulsed arc discharge method, and their characterization by various spectroscopic measurements, including TEM, XRD, SQUID, FT-IR, etc. Tumor cell targeting ability was introduced by surface modification of these carbon nanoparticles with folate moieties.

Biocompatibility of polymer grafted core/shell iron/carbon nanoparticles

For biomedical applications, emerging nanostructures requires stringent evaluations for their biocompatibility. Core/shell iron/carbon nanoparticles (Fe@CNPs) are nanomaterials that have potential applications in magnetic resonance imaging (MRI), magnetic hyperthermia and drug delivery. However, their interactions with biological systems are totally unknown. To evaluate their potential cellular perturbations and explore the relationships between their biocompatibility and surface chemistry, we synthesized polymer grafted Fe@CNPs with diverse chemistry modifications on surface and investigated their dynamic cellular responses, cell uptake, oxidative stress and their effects on cell apoptosis and cell cycle. The results show that biocompatibility of Fe@CNPs is both surface chemistry dependent and cell type specific. Except for the carboxyl modified Fe@CNPs, all other Fe@CNPs present low toxicity and can be used for further functionalization and in a wide range of biomedical applications.

Facile surface functionalization of nanodiamonds

Nanodiamonds (NDs) have versatile applications in electro-optical devices, sensors, and biomedicine. Owing to the difficulty in activation of the inert sp(3) C-H bonds on the surface of NDs, it is not trivial to modify the surface functionalities on NDs. A few functionalization methods have been reported in the literature for surface modification of NDs. Many of them, however, are either multiple steps/time-consuming, or require the use of highly toxic/environmentally unfriendly reagents, such as fluorine gas and sulfuric acid. It is necessary to develop a simple process for surface functionalization of NDs to have both hydrophobic and hydrophilic functional groups. In this report, a facile process was developed to allow easy and rapid surface modification of NDs to become dispersible in either water or organic solvents using the same process. The process involves surface graphitization of NDs, followed by radical initiated surface grafting of oligomers with various functionalities, including -C(=O)OCH(3), -COOH, -NH(2), or aliphatic moieties.